Food chemistry

Definition:Food chemistry, the largest branch of food science, is the study of the basic biological components of food, including the interactions and processes involving lipids, carbohydrates, and proteins. The field also includes the understanding of nonbiological components—such as preservatives, additives, or flavorants—and their effect on manufactured foodstuffs. A food chemist is charged with improving the taste and quality of food, the development of packaging that safely preserves food, and studying the effects of industrial processing on the vitamin and mineral contents of food.

Basic Principles

Food chemistry can be dated to the eighteenth century, when a Swedish pharmacist named Carl Wilhelm Scheele (who discovered chlorine, glycerol, and oxygen) studied the properties of lactose. By the time Scheele died in 1786, he had isolated a number of chemical compounds found in plants and animals. However, the study of food chemistry as a means to create new food products did not arise until a century later. Most food chemistry institutions, including the Journal of Agricultural and Food Chemistry, published by the American Chemical Society, and the Institute of Food Science and Technology in London, were established in the 1950s.

Food chemistry requires a strong understanding of the principles of biochemistry. The two fields are built on the study of chemical compounds known as macronutrients, which include carbohydrates, proteins, and lipids (more commonly known as fats). Cells use these macronutrients as a source of chemical energy. Food is primarily made up of these three components. An understanding of the interactions of these three components provides the basis for home cooking as well as the manufacture of food products on a large scale. For instance, fats like meat or milk can go sour because of the chemical makeup of lipids and the effects of oxidation. Food chemistry also encompasses an understanding of water, vitamins, minerals, and enzymes.

Core Concepts

In addition to the organic chemical compounds that occur in food, food chemistry makes use of concepts from several other subjects, including: food rheology, food fortification, aseptic processing, and water activity.

Food Rheology. The study of rheology examines the movement and flow of unusual materials, like mayonnaise or peanut butter. Rheology also applies to nonfood substances like paint or molten plastic. Rheology as it applies to food is particularly important when it comes to processing. When developing a product, food chemists need to think about how that product might behave within the structure of a package and in transport. In addition to the logistics of a product, rheology dictates much of the consumer experience, including the texture of a product and how it feels to the mouth (referred to as the “mouthfeel”). For instance, is that product juicy, smooth, brittle, or creamy? Rheology is also involved in a food’s structure and appearance, as well as the characteristics of the food’s components. Does a particular food product contain a paste? Can it retain its shape? All of these characteristics relate to a food product’s rheology.

Food chemists (and food rheologists) aim to develop instruments of production that address the complexity a food’s rheological behavior. In this way, industrially produced foods with unusual textures can be manufactured to taste and feel the same from factory to consumer.

Food Fortification. Food fortification, or enrichment, is the addition of essential vitamins, or micronutrients, to a food product. Food fortification was first practiced in the 1920s after two Ohio doctors found that sodium iodine was effective in the treatment of goiter (an enlarged thyroid gland). This discovery led to the introduction of iodized salt, which has become commonplace, as have fortified foods in general. Today, for example, you can buy milk that has been fortified with vitamin D. Food fortification is becoming a matter of public health policy as well as a commercial endeavor. In developing countries, several companies are working to fortify staple foods, like grains, with vitamin A; the staple foods in these countries lack proper nutrients due to either the poor quality of soil in the region or an insufficient diet nationwide. The World Health Organization (WHO) cites micronutrient deficiencies as the cause of blindness, anemia, and intellectual development challenges in children. In 2003 the Global Alliance for Improved Nutrition (GAIN) announced that they would assist recipient countries in fortifying foods and condiments like salt, flour, oil, sugar, and soy sauce with iron, iodine, vitamin A, and folic acid.

There are four methods commonly used in fortifying foods. The first is biofortification, or the process of breeding genetically modified crops to increase their nutritional value. Microbial biofortification, or synthetic biology, is the addition of probiotic bacteria to foods. Commercial fortification refers to the processes that create the products at the grocery store, including fortified milk and salt. Lastly, home fortification can be achieved by the application of drops containing micronutrients like vitamin D.

Aseptic Processing. Aseptic processing refers to the process of safely packaging food products to ensure that they are kept fresh. Philip Nelson, a professor of food science at Purdue University, developed the modern process in which foods are sterilely processed and then placed in a similarly sterile container. (Aseptic processing was used before Nelson, but he was the first to apply it on a larger scale.) Nelson made it possible for companies to process foods, namely liquids and semiliquids like pudding, safely and at a much faster rate. During aseptic processing, the food product passes through a very thin pipe where it is quickly heated (to kill pathogens) and then quickly cooled. After passing through the pipe, the food product is packaged in a pressurized and pathogen-free compartment.

The old method, which Nelson’s has largely replaced, required a larger amount of energy to heat the food product after it had already been packaged; companies also ran the risk of ruining the product if left in the heat for too long. Still, the inception of aseptic processing, which began in the wine industry at the turn of the twentieth century, has ensured that food products, from canned soup to orange juice, can be mass-marketed safely.

Water Activity. Another important element of food chemistry is water activity. Water activity is widely defined as the measure of free or unbound water available for chemical or biological activity. The amount of water a food contains influences the food’s texture and, in some cases, how susceptible it is to spoilage or the growth of microbes. Food chemists are able to remove water through concentration, or through freezing, salting, or drying a food product. These methods are helpful in food processing.

Much as the interactions of carbohydrates, proteins, and lipids are the building blocks of food chemistry, water’s interactions with a food’s chemical makeup has an extraordinary influence on the properties of that food. Food in which water is tightly bound to surrounding protein molecules has a very low water activity; foods with low water activities include crackers and dried vegetables. Fresh fruit is an example of food that has a high water activity. Moisture allows for the rapid growth of bacteria, which is why fresh fruit left out for too long will soften and attract insects. The mathematics of water activity is not useful for frozen foods, but is widely used for dried, salted, and fresh foods.

Applications Past and Present

Food Preservation. The earliest endeavors in food chemistry were in an effort to preserve food. In the early 1800s, the French chef Nicolas Appert answered a challenge from French emperor Napoleon Bonaparte to invent a way to keep food from spoiling when being shipped to the French army. After years of experimenting, Appert found that if he sealed food in an airtight container and then soaked that container in hot water, food would stay fresher for longer periods of time. Appert’s discovery, of course, was the canning technique that would affect food consumption worldwide. (An Englishman named Peter Durand was the first to apply Appert’s technique to tin cans; Appert had used glass bottles.)

Of course, humans had been preserving or slowing the fermentation process of food for thousands of years by drying, smoking, salt-curing, or salt brining meats and vegetables to be consumed later or out of season. Early American settlers handed down techniques for home canning, pickling, and making jam. In the 1800s, Americans made use of cellars and occasionally caves as an early means of refrigeration. At the turn of the twentieth century, New York inventor Clarence Birdseye discovered that flash-freezing foods preserved their taste better; Birdseye found a way to effectively deliver these frozen foods to the public, creating a precursor to the extensive modern frozen food industry.

The visible effects of temperature on food were understood early, but even Appert was not entirely sure why the food he had sealed in bottles (and then heated) did not go bad. The first person to fully understand why certain foods were susceptible to spoilage and under what conditions was French chemist Louis Pasteur. Pasteur realized that microorganisms were responsible for spoiling food and causing illness. His contributions to food chemistry are more fully discussed in the next section.

Food Safety. Louis Pasteur took a more scientific approach to food less than fifty years after Appert fed Napoleon’s army. He discovered that bacteria were responsible for souring the wine and beer made by local alcohol manufacturers in Lille, France. Pasteur reasoned that heating a liquid to just below its boiling point and then cooling it would kill bacteria. He later famously applied this approach to milk, and the process came to be known as pasteurization. Pasteur recognized that bacteria came from the environment (and further, that when food was left in the environment, it was susceptible to that bacteria) at a time when most scientists thought that bacteria spontaneously generated.

In 1888, during an outbreak of meat poisoning in Germany, August Gärtner discovered a food-borne bacterium called Bacillus enteritidis. It seemed that people were getting sick after consuming meat from a cow that had been sick when it was slaughtered. Gärtner’s discovery influenced what safety precautions are taken when food is processed. Consumers and producers were more educated about food safety at the dawn of the Industrial Revolution, but it became clear that there would need to be public policies put in place to address the expansion of the business of food.

The United States enacted two historic pieces of public health legislation in 1906 when Congress passed the Pure Food and Drug Act and the Meat Inspection Act. The Pure Food and Drug Act is a testament to the work of journalists, including author Upton Sinclair and a government official named Harvey W. Wiley. Journalists known as muckrakers raised public awareness of careless food preparation and questionable business practices in the food industry. Sinclair’s novel The Jungle was published in 1906; it shocked the nation with horrific descriptions of the Chicago meatpacking industry. Wiley, who had been commissioned to research the adulteration of food products in 1902, presented further evidence that poisonous and harmful additives were being used by food companies to meet demand. President Theodore Roosevelt passed the Meat Inspection Act the same year. The Pure Food and Drug Act was amended several times before being extended in scope in 1933.

The US Food and Drug Administration (FDA)—first created as the Bureau of Chemistry in 1862 by President Abraham Lincoln—and other regulatory agencies continue to monitor the food industry as the processes of food production continue to change.

Food Technology. Food technology refers to the actual production processes of food. Though the term is relatively new, scientists have been contributing research to the field for centuries. Appert and Pasteur can be credited as early innovators in modern food technology; canning and pasteurization are processes that are widely used today, though they have also been improved. As the twentieth century progressed, people enjoyed better public health information and were able to store food for longer; it then became the endeavor of food technologists, as mass-marketed foods were on the rise, to also improve a product’s overall quality and taste.

The 1940s saw a boom in the mass production of food during World War II. Like Appert and his glass bottles, practices were invented to satisfy wartime needs and then later applied commercially. Companies developed ways of concentrating, freezing, and drying foods (such as frozen concentrated orange juice) to ship overseas. Flour was fortified with iron as the country survived on rations, and an early form of aseptic processing came into use. The same era also gave rise to homogenized milk, which is blended intensively so that the fat does not separate. In the 1950s, controlled atmosphere packaging (CAP) was developed to ensure a longer shelf-life for products. Mechanized food production reigned. In the 1960s, the bottling industry put local soda fountains out of business by selling popular beverages—like Coca-Cola, developed by a pharmacist in the late 1800s—at the grocery store. Mechanization led to a boom in processed foods, some of which contained synthetic or chemically enhanced ingredients.

Trans fat, largely in the form of partially hydrogenated vegetable oil, became popular with producers in the early 1900s because it served as a preservative, giving food products a longer shelf-life; consumers liked it because it tasted good, and often improved a product’s texture. It was not until the 1990s that scientists found that trans fats can cause health problems like high cholesterol, heart disease, and diabetes. Along with such information came a wealth of diet products—Healthy Choice began selling frozen dinners in the late 1980s—and products that purported to be healthy imitations of the real thing. Artificial sweeteners, which are generally seen as safe, are added to a number of food products in lieu of sugar. High fructose corn syrup, a sweetener often used in soda, has yielded mixed results in terms of its health costs and benefits.

The chemistry of food is often seen as the realm of food companies and researchers, but as the public demands more information about the contents of what they consume, food chemistry continues to expand in scope.

Molecular Gastronomy.Molecular gastronomy is a modern style of cuisine that emphasizes the chemical transformations that take place during the cooking process. The discipline is relatively new; it was founded in 1992 by two scientists, Hervé This and Nicholas Kurti, and touts itself as part science and part art. Molecular gastronomy is often called culinary alchemy for its surreal juxtapositions that include hot ice cream, spherical ravioli, and olive oil foam.

Hervé This presented his dissertation on molecular gastronomy at the University of Paris in 1996. According to his paper, This identified five goals of the new science. The first goal was to “collect and investigate old wives’ tales about cooking.” The second was to “model and scrutinize existing recipes,” and the third was “to introduce new tools, products, and methods to cooking.” As a fourth goal, This hoped to “invent new dishes using knowledge from the previous three aims.” And finally, his fifth goal was “to use the appeal of food to promote science.”

Molecular chefs make use a number of “ingredients” that can be found in a lab, including liquid nitrogen and chemicals like carrageenan (seaweed extract), maltodextrin (a sweet additive made from starch), and xanthan gum (a food-thickening additive).

Social Context and Future Perspectives

The growth of the food industry and industries producing food products has been exponential over the course of the last century. Science as it relates to food became a fully fledged field of study only sixty years ago—though, as stated in the above descriptions, research pertaining to food and food chemistry was being conducted long before that.

Much like Pasteur, whose observations of fermentation and subsequent invention of pasteurization changed the way scientists and consumers understood food-borne illness and disease, innovations in the food industry today are rapidly being applied to the pharmaceutical industry and even to the development of biofuel. Food chemistry of the twenty-first century is no longer limited to the logistics of manufacturing sliced bread. Food chemistry today is applying new principles and technology to feed developing nations and to ensure that industrialized ones are practicing safe methods of food production. The latter is not an easy task in a world where food is often consumed for its convenience rather than its nutritional value. Food chemists must ensure that all food products—from fast-food hamburgers to pesticide-free vegetables—are safe for all consumers.

Proponents of food fortification—first practiced in the United States during World War II and now in places like rural China and Vietnam—understand that food not only affects health and productivity, but can also make consumers sick. As we move into the next phase of a growing field, the food chemists of the future are regarded by many as part of the solution to an ailing world.

Bibliography

Belitz, Hans-Dieter, Werner Grosch, and Peter Schieberle. Food Chemistry. 4th rev. ed. Munich: Springer, 2009.

Coultate, Tom P. Food: The Chemistry of Its Components. 5th ed. Cambridge: RSC Paperbacks, 2009.

"Dieticians and Nutritionists." Occupational Outlook Handbook, Bureau of Labor Statistics, May 2022, www.bls.gov/ooh/healthcare/dietitians-and-nutritionists.htm#tab-6. Accessed 25 Sep. 2023.

"Food." United States Food and Drug Administration, www.fda.gov/food. Accessed 25 Sep. 2023.

"Food: A Chemical History." Science Museum, 27 Nov. 2019, www.sciencemuseum.org.uk/objects-and-stories/chemistry/food-chemical-history. Accessed 25 Sep. 2023.

"Food Science & Agricultural Chemistry." McGill University, libraryguides.mcgill.ca/food-science. Accessed 25 Sep. 2023.

About the Author

Molly Hagan, BFA, is a freelance journalist and writer for Current Biography magazine. She has written the biographies of well-known economists, physicists, climatologists, and mathematicians, among many others. She conducted interviews for an in-depth profile of neuroscientist and pioneering researcher Dr. Daniela Schiller of Mount Sinai Hospital in New York.